How Do You Winterize Delphiniums? (Winter Preparation)

So, winter’s coming and you need to prepare your delphiniums for the cold weather.

Delphiniums are a flowering perennial plant from the Ranunculaceae family.

Similar to other plants that don’t tolerate the cold well (I’m looking at you, caladiums), you’ll need to give them some extra care so they make it to spring.

Winterize and prepare delphinium for the winter.

There are over 300 species of perennial flowering plants, and this one is just one of them.

Thankfully, it’s pretty easy to save them and prep them for winter.

You’ll learn everything you need to know to winterize your delphiniums for the cold season.

And if you have any questions, drop a comment after the article.

How do you prepare delphiniums for the winter?

Delphiniums need to be prepared for winterizing if you live somewhere cold (By KENPEI – KENPEI’s photo, CC BY-SA 3.0).

Wintering delphiniums is a necessary practice if you live in an area where the nights are freezing.

Protecting them until next spring provides shelter for them to bloom once again when the winter is over.

Although delphinium is a hardy plant and relatively low maintenance, you should still protect and winter the plant properly.

Preparing them for the winter is easy (thankfully) so it shouldn’t take you too much time. This will then bring you a blossom of color when the temperature rises again next year.

Wintering delphiniums is a process. There are a few different things you can do to shelter the plant depending on your hardiness zone.

Watering delphinium during dormancy

Delphinium needs to be watered regularly. When the soil gets solid after freezing, use a hose to trickle water the root system.

You can press the nozzle of the hose right up against the stalk of the plant to do this. If you can’t get in there, use a small shovel to dig up the soil around the stem and loosen it.

The plant continues to drink the water even if frozen and will lose moisture through the leaves.

Keep the soil damp, but don’t overdo it.

When should I cut down my delphiniums after flowering?

Cut down spent flowers after all blooms have faded.

Deadhead your plant and remove any spent stalks. Keep the side shoots after blooming. This will help conserve energy for the new flower stalks.

You can safely cut the stalks right where the leaves start to branch out.

Do this when the blooms have faded and no longer are possible. By pruning the stalks of the plant, it can focus its energy on the shoots instead.

If you cut the stalks early, this will disrupt a possible bloom, so only trim when you’re sure that the plant blooms have completely faded. The easiest way to tell is when the leaves have begun to yellow.

Side shoots will be visible, but they shouldn’t be pruned. Leave those alone.

If done correctly, next spring will bring you a fresh bouquet of color. New side shoots will sprout and grow up with a fresh pick of color.

The stalk will look nearly dead after you’re done purging, but this is normal.

Don’t fret. Just keep it this way until winter.

Trimming the plant

Delphinium needs to be pruned down to 8” max after the first autumn frost.

This will make it easier to manage and mulch. I prefer doing this to keep it tidy, but it’s your choice.

If you don’t trim the plant down to just a few inches, the plant becomes unkempt and attracts pests throughout its dormancy over the winter.

Remove weeds

Weeds will compete with your delphiniums, so you’ll want to remove them wherever you spot them.

Also, get rid of any clutter or competing plants to maximize your next bloom.

You should also take this time to declutter your flower beds and remove any debris.

This will get you a nice, gorgeous bunch of delphiniums when spring rolls around.

Watch for pests

When delphiniums enter their dormancy period over the winter, they’re prone to pests.

So you’ll want to monitor them and check in once in a while to make sure aphids and other common garden pests aren’t eating them up.

They’re defenseless during dormancy and aphids will gladly feast on the foliage. If you spot any pest activity, trim off the infected foliage and create a pest control plan.

Aphids wreck havoc on delphiniums as they’re tolerated in the cold winter, so even the chill outside won’t stop them from eating your plants.

You’ll want to check for them now and then to protect your delphiniums from wintertime pests.

Slugs, snails, and other creepy crawlies will be searching for your delphinium during dormancy.

Be on the lookout for these bugs so they don’t destroy your defenseless plant.

Protect delphiniums from frost

When the temperature drops too low, your delphiniums are prone to frost.

You can help protect them from the chill by adding some high quality, organic mulch.

Simply sprinkle it around the stalk to offer a layer of insulation against the winter chill.

Delphiniums are somewhat hardy to cold temperatures, but when the nighttime climate drops below -30F, you should take measures to protect your plants. Think of the mulch as a nighttime sweater for your plants!

If you don’t have mulch, you can also use shredded pine needs, chopped leaves, newspaper, straw, or hay.

Grass also makes a nice substitute, but if the grass seeds get into your flower bed, they’ll compete with your delphiniums for precious nutrients.

This may stunt their growth next spring.

So only use grass that you trust. Mulch helps protect your delphiniums from the cold, chill, and even snow. The soil is kept in place and even temperature fluctuations pose little threat to a properly mulched plot.

Mulch makes an excellent barrier against freezing and thawing cycles and holds in moisture which your delphinium desperately needs during this time.

se a high-quality organic mulch and apply 3” in the autumn when the soil is starting to become cooler.

Do you cut back delphiniums in the fall?

A beautiful blue delphinium plant bloom.
You sure can.

Yes, this is the optimal time to prune your delphiniums to prepare it for the winter.

The plant stalks can be cut back by removing the entire plant down to the basal leaves after all blooms have faded. It should be pruned down to 6-8” when complete.

Leave the remaining plant rooted in the soil and prepare it for the coming winter.

Do delphiniums die back in winter?

Delphiniums are a perennial plant and hardy to cold temperatures.

They can tolerate recorded temperatures as low as -30F (hardiness zone 3). They die back completely in late autumn, which is when you should help prepare the plant for the cold season.

Delphinium returns and grows back in the spring.

You can protect and shelter your plant to give it the best blooms possible next season by preparing it for the winter- this is known as “winterizing delphinium.”

Is delphinium poisonous to touch?

Delphinium is a poisonous plant that should not be handled directly without proper equipment.

You’ll need long-sleeved clothing, study gardening gloves, and goggles for starters. If you touch delphinium, you may get some skin irritation.

The plant contains poisonous compounds like methyllycaconitine and diterpenoid alkaloids. Delphinium seeds are also toxic

Don’t touch the plant directly and never ingest it.

Delphinium is also unsafe for dogs and other pets. This is NOT something to ignore, as the plant can cause a severe reaction in humans which can be lethal.

Always exercise extreme caution and never handle one directly if you don’t know what you’re doing.

Further reading

These references may be useful for delphinium care:

Did you prepare your delphinium for winter?

Delphinium winterized.
Did you get your plant ready for the winter?

You should now know exactly how to protect your plant over the winter.

By doing some basic TLC, you can ensure that your delphinium will be back to greet you with its gorgeous color and blooms next spring.

Although these plants are hardy, they do need some rest during the cold winter hibernation.

Have you prepared them yet? Do you have any tips?

Let us know by posting a comment below and providing your thoughts with fellow readers!

Now go save your delphinium!

1 thought on “How Do You Winterize Delphiniums? (Winter Preparation)”

  1. Leslie Jirouschek

    Hi,
    I have three pots of delphiniums that I never got around to planting last summer. Can I put them outside against the house on our deck and then plant in spring? Or, must I keep them inside (laundry room) until I can get them in the ground? We are still getting very cold/freezing nights (zone 6b) and I don’t want to lose them. How can I start to get them used to being outside and when should I do that?
    I am new to delphiniums, and found out they are the flower of my birth month (July) – pretty cool. Mine are blue flowering and about 3′ in height. They will eventually be planted up against the barn in a raised garden, along with some foxglove and daisies (preferably the kind the deer don’t eat!) Also, when is the best time to plant them? I’m thinking May ? Appreciate your feedback as being a beginner with these plants I want to make sure I do this correctly.
    Thanks,
    Leslie

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